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LambdaCalcParser.scala
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LambdaCalcParser.scala
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/*
* Copyright (c) 2021, Daniel Spiewak
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. Neither the name of the copyright holder nor the names of its contributors
* may be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package lambdacalc
import scala.collection.compat.immutable.LazyList
import scala.collection.mutable
import com.codecommit.gll._
import AST._
object LambdaCalcParser extends common.Example[(List[Alias], Expr)] with RegexParsers {
// %%
lazy val aliases = (alias+) ~ "-{3,}".r ~ expr ^^ { (a, _, e) => (a, e) }
lazy val alias = x ~ "=" ~ expr ^^ { (id, _, e) => Alias(id, e) }
lazy val expr: Parser[Expr] = (
"\\" ~> x ~ "." ~ expr ^^ { (id, _, e) => Lambda(id, e) }
| exprNoLam
)
lazy val exprNoLam: Parser[Expr] = (
exprNoLam ~ exprNoApp ^^ App
| exprNoApp
)
lazy val exprNoApp = (
"(" ~> expr <~ ")"
| x ^^ Val
)
val x = """[^\s\.\\()=;]+""".r ^^ { id => Symbol(id) }
// %%
def parser = aliases
def handleSuccesses(forest: LazyList[(List[Alias], Expr)]): Unit = {
val errors = mutable.Set[String]()
val status = for ((tree, expr) <- forest) yield {
try {
val env = tree.foldLeft(scala.collection.mutable.Map():Env) { (env, alias) =>
env(alias.id) = alias.expr.eval(env)
env
}
Some(expr.eval(env))
} catch {
case EvalException(msg) => {
errors += msg
None
}
case _: StackOverflowError => {
errors += "stack overflow"
None
}
}
}
val results = status flatMap { x => x }
if (results.length == 0) {
for (msg <- errors) {
println(" runtime error: " + msg)
}
} else if (results.length == 1)
println(" " + results.head)
else
printf(" parse error: Ambiguous parse: %s valid trees%n", results.length.toString)
}
}